The present invention generally relates to a control system for lifting and lowering the body of an air-suspended vehicle. With such systems, the desired distance between the body of the vehicle and the axle of the vehicle may be automatically adjusted. Additionally, it may be desired to design the system in a way that the body may be lifted and lowered, respectively, in an arbitrary way. Such an arbitrary adjustment may serve to adapt the height of the vehicle to the height of a loading platform to load or to unload the vehicle. The control system may also be designed in a way that different heights of the body with respect to the axle may be stored for later use. The system may be applied to motor vehicles as well as to trailers.
A control system is known from German Patent No. 35 06 179 C2 The known control system includes a level control valve which serves to adjust the desired distance between the body and the axle of the vehicle when the system works correctly. The level control valve is combined with a path sensor to form one common unit. The path sensor sends an electric signal to an electronic control unit, the electric signal corresponding to the distance between the body and the axle of the vehicle. A switching valve unit is arranged downstream of the electronic control unit, the switching valve unit including a switching valve having four positions, namely a lifting position, a lowering position, a driving position and a stop position. The switching valve is designed in a two circuit way, meaning it serves to operate two air-suspension bellows, or two air-suspension bellow circuits. The electronic control unit is connected to a selector switch such that it allows for arbitrarily lifting and lowering the body. Arbitrarily lifting or lowering the body with respect to the axle may be desired to adapt the height of the vehicle to an existing loading platform, for example. Arbitrarily lifting and lowering the body of the vehicle is only possible during correct electric power supply of the known control system. Since electric supply usually is interrupted when trailers are parked at a loading platform, arbitrarily lifting and lowering is then no longer possible with the known system. In the case of power supply being interruptedxe2x80x94no matter whether this occurs due to a defect or consciously caused by the userxe2x80x94the switching valve of the known system remains in its present position. Consequently, the body cannot be lifted or lowered with respect to the axle in the known system. In the known system, this problem concerning a trailer being parked at a loading platform can only be solved by making sure that there always is correct electric power supply of the known control system.
Another control system for lifting and lowering the body of an air-suspended vehicle including level control is known from German Patent Application No. 43 27 764A1. The vehicle additionally includes a lifting axle. The known control system includes an electronic control unit including a switching valve unit. The switching valve unit includes a plurality of switching valves to be electrically controlled and to be controlled by a spring. The known arrangement is chosen such that the position of the switching valves that has been electrically caused is maintained even without power supply. In this way, the lifting axle remains in its present position even when power supply is turned off, or when power supply fails. In this way, reduced consumption of power is achieved. However, when power supply fails, lifting and lowering of the body of the known vehicle is not possible.
The present invention relates to a control system for lifting and lowering the body of an air-suspended vehicle. The vehiclexe2x80x94which may be a motor vehicle or a trailer, for examplexe2x80x94includes an axle and level control. The system includes a source of compressed air, a plurality of air-suspension bellows each being associated with at least one axle and being designed and arranged to adjust a desired distance between the body and the axle, a path sensor being designed and arranged to sense and determine the distance between the body and the axle and to create and deliver a respective electric signal, a switching valve unit having a lifting position, a lowering position, a driving position and a stop position, an electronic control unit being designed and arranged to control the switching valve unit in response to the electric signal delivered by the path sensor, a first conduit branch being located between the source of compressed air and the air-suspension bellows, a second conduit branch being located between the source of compressed air and the air-suspension bellows, at least one level control valve being located in the first conduit branch, and at least one locking valve being located in one of the conduit branches and including a spring, the locking valve being designed and arranged to be electrically switched to reach a first position and to be switched by the spring to reach a second position. The first conduit branch is designed and arranged to be activated in the second position, and the second conduit branch being designed and arranged to be activated in the first position. The present invention also relates to a controlling installation and to a control apparatus for lifting and lowering the body of an air-suspended vehicle.
The novel control system may also be used on trailers, and it is designed to be automatically active even when there is no power supply. It is important that the locking valves may be electrically switched to reach a first position, and that they may be mechanically switched to reach a second position. In this way, the first (xe2x80x9celectricalxe2x80x9d) position is only taken during correct power supply, while mechanical-pneumatic operation is used during interruption of power supply. The second position is the fallback position, orxe2x80x94in other wordsxe2x80x94the fallback plane. Depending on the fact whether the control system operates electrically or mechanical-pneumatically, the respective other conduit branch is caused to be ineffectivexe2x80x94or at least its effects are substantially reducedxe2x80x94in a way that it does not have a substantial influence on the compressed air prevailing in the air-suspension bellows. The locking valve has two positions of which one is a locking position in which the connected parts of the conduits are locked with respect to one another. The second position is a passage position or a release position in which the respective connected conduit parts are interconnected.
A first embodiment of the novel control system includes a locking valve being located in the conduit branch upstream or downstream of the level control valve. This locking valve has a passage position to be caused and adjusted, respectively, by a spring, and a locking position to be electrically adjusted. It is especially preferred to arrange the locking valve downstream or after the level control valve such that the switching valve unit may be arranged in the other conduit branch. The first conduit branch in which the level control valve is arranged and which may extend to the air-suspension bellows is locked during correct power supply such that the switching valve unit may operate the air-suspension bellows without any loss of air. However, it is also possible to arrange the locking valve in the first conduit branch in which the level control valve is arranged and upstream or in front of the level control valve. A slight loss of compressed air occurring at the level control valve due to pushing movements and vibrations during travel of the vehicle is acceptable.
Another possibility is to arrange the locking valve in the second conduit branch in which the level control valve is not arranged. The locking valve then has a locking position to be caused by the spring, and a passage position to be electrically adjusted. When the locking valve is arranged in the conduit branch in which the level control valve is not located, it has to have an inverse design in a way that its positions are designed to be controlled in an inversed way. The electric control is associated with the passage position such that the level control valve is by-passed or evaded during correct power supply. On the other hand, when power supply fails, or when power supply is interrupted, the by-pass conduit of the level control valve is locked such that the level control valve automatically fulfills its mechanical-pneumatic function.
It is also possible that there are two locking valves, each of the locking valves being arranged in one of the two conduit branches. The two locking valves each have a locking position and a passage position. The passage position of the locking valve being arranged in the conduit branch in which the level control valve is arranged is designed to be adjusted by the spring. The passage position of the other locking valve is designed to be electrically adjusted by the electronic control unit. The achieved double arrangement of two locking valves each being located in one of the conduit branches is more complicated than the single design, but it also capable of realizing the desired function with a fallback position. Furthermore, the double design arrangement prevents the level control valve from consuming air during correct power supply. It is still possible to chose the lengths of the conduit branches to be longer or shorter. The two conduit branches usually start directly after the source of compressed air, meaning close to a compressed air reservoir or the like. The branch location being associated with the air-suspension bellows may be arranged at different distances with respect to the air-suspension bellows. It is also possible to arrange a two way valve at this branch location to prevent backflow at this position.
Furthermore, it is possible that a common locking valve is arranged at the branch location of the two conduit branches close to the source of compressed air. The common locking valve in the position to be switched by the spring connects the source of compressed air with the conduit branch in which the level control valve is arranged, and it locks the other conduit branch. In the position to be reached by switching the electric control unit, the common locking valve connects the source of compressed air with the conduit branch in which the level control valve is not arranged, and it locks the conduit branch in which the level control valve is arranged. Such a common locking valve fulfills the functions of two locking valves each being located in one of the two conduit branches. It may have a structurally advantageous design by only including two positions. In the first position, the first conduit branch is supplied with compressed air, and the second conduit branch is locked. In the second position, the first conduit branch is locked, and the second conduit branch is supplied with compressed air. Accordingly, electric control and control by the spring are respectively associated.
It is also possible that a common locking valve is arranged at the branch location of the two conduit branches next to the air-suspension bellows. The common locking valve has a first position to be switched by the spring in which the conduit branch in which the level control valve is arranged is connected to the air-suspension bellows, and the other conduit branch is locked. In the second position to be switched by the electric control unit, the common locking valve connects the conduit branch in which the level control valve is not arranged to the air-suspension bellows, and it locks the other conduit branch. In this way, the common locking valve may also be arranged at the other branch location of the two conduit branches, meaning at the side of the air-suspension bellows.
All the above described embodiments may be combined with a switching valve unit including two switching valves being arranged in series. The two switching valves are designed to be switched electrically and by a spring. Due to the arrangement of the two switching valves in series, there is a sufficient number of the different combinations of the lifting position, the lowering position, the driving position and the stop position. The switching valve unit may be arranged in the conduit branch in which the level control valve is not arranged, or in a common conduit being located downstream and leading to the air-suspension bellows.
Furthermore, it is possible that the switching valve unit includes a switching valve at least having three positions, meaning a lowering position, a lifting position and a position which is the stop position and the driving position at the same time. The switching valve is designed to be switched electrically and by a spring. These three positions of the switching valve are sufficient since the stop position and the driving position are combined as one position. Such a design is advantageous since there is no consumption of air when the vehicle is driven and when there is correct power supply and correct distance between the body of the vehicle and the axle of the vehicle. In all exemplary embodiments, it is important that the locking valve as well as the switching valve unit are designed to be switched by a spring to reach a certain position corresponding to the fallback position, meaning the position which is active during interrupted power supply.
Furthermore, it is possible that the switching valve and the locking valve are designed as one common structural unit. Such an arrangement is especially advantageous, and it may be produced at low cost. The arrangement of the two conduit branches and a common valve unit fulfilling the functions of the switching valve and the functions of the locking valve are only required. The level control valve may be designed to include the path sensor, meaning the path sensor is integrated into the level control valve. On the other hand, it is also possible that the level control valve and the path sensor are not designed as one common structural unit, meaning they may be designed as separate units. In all cases, the electric signal to be created and transmitted by the path sensor is processed by the electronic control unit.
In all the above described exemplary embodiments, the switching valve unit may be located in the conduit branch in which the level control valve is not located. On the other hand, the switching valve unit may also be located downstream or after the branch locationxe2x80x94or, in other words, the junction locationxe2x80x94of the two conduit branches or line branches, meaning directly upstream of the air-suspension bellows.
Furthermore, it is possible that the two xe2x80x9cparallelxe2x80x9d conduit branches are joined by a two way valve, and that the switching valve unit is located in a common conduit leading to the air-suspension bellows. The two way valve fulfills its known function, meaning it transmits the increased inlet pressure towards the outside.
It is especially advantageous if the electronic control unit is designed to process an electric signal corresponding to the driving condition of the vehicle. Such an electric signal usually is supplied by an antilock system (ABS) or an electronic brake system (EBS), and it may be processed and used in the electronic control unit. The electronic control unit may be designed as a separate unit, or to be structurally combined with the electronic control unit of the ABS system or of the EBS system.
In all cases, it is possible that the level control valve and the path sensor are designed to form one common unit. Such integrated designs are known in the art. However, they are not used in combination with usual electric actuation and pneumatic-mechanical actuation as a fallback position. In the case of such a structural combination, the existing actuation drive of the level control valve may be simultaneously used as the mechanical component of the path sensor.
Furthermore, there is the possibility of the electric control unit including a selector switch and/or a control valve for arbitrarily lifting and lowering the body of the vehicle being located in the conduit branch in which the level control valve is arranged. The control valve is designed to be manually operable. Such a selector switch fulfills the function of allowing for arbitrarily lifting and lowering the body of the vehicle during correct power supply. The selector switch may also be designed to fulfill additional functions, for example, to store a second height of the body of the vehicle with respect to the axle of the vehicle or the like. Correspondingly, a control valve being manually operable is arranged in the conduit branch in which the level control valve is arranged. The control valve is designed and arranged to realize similar functions in the fallback position.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and the detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.